1. Technical Field
The present disclosure relates to a control device, an imaging apparatus and a control method.
2. Description of the Related Art
Nowadays imaging apparatuses using semiconductor sensors are utilized in various fields. For example, in X-ray imaging apparatuses for medical or industrial purposes, a method of using an X-ray detector in which a phosphor and a large-area amorphous silicon (A-Si) sensor are brought into close contact with each other and enabling an X-ray image to be directly digitalized without involving, for example, an optical system is in practical use.
In current use of X-ray sensors, an amplification unit and a drive mode switching unit (switch unit) corresponding to a drive mode are provided in each pixel by using a single crystal image sensor such as silicon. Japanese Patent Application Laid-Open No. 2003-134396 discusses a technique for providing a plurality of source follower amplifiers with different gate sizes for each pixel in an X-ray sensor. According to this technique, in a low-dose imaging mode, a source follower amplifier with a small gate size is selected for all pixels of the sensor, so that the sensor can be made highly sensitive. On the other hand, in a relatively high-dose imaging mode, a source follower amplifier with a large gate size is selected for all pixels of the sensor, so that imaging with a low noise and a wide dynamic range can be realized,
However, when the amount of radiation received by the X-ray sensor is largely different for each pixel of the sensor, there is an issue in that saturation or input/output characteristics may be deteriorated for certain pixels which receive a large amount of light, whereas contrast will become low in pixels which receive a small amount of light. Therefore, when the received radiation is largely different among pixels, good contrast could not be obtained while reducing the saturation in the entire image.